Drilling apparatus



April 29, 1941. .1. F. CHAPPELL DRILLING APPARATUS Original Filed May 25, 1936 3 Sheets-Sheet l gram (James A 6775230 el/ A an-H29, 1941'- J. F. CHAPPELL I DRILLING APPARATUS Original Filed Ra 25, 1936 s sheets-sheet 2 c/ames l. C/ra a ae Patented Apr... 29, 19M

f1 fill arcane anama nrrannirns James F. Chappell, Mineolla, Tern, assignor to vclllliappelll Draining Equipment @orporation, a

corporation of Texas Original application in, 25, was, Serial No. 81,647. Divided and this application ilprii lid, 1938, Serial No. zciscs an improved drilling apparatus wherein the drill pipe or stem forms the well casing, whereby the usual casing is eliminated.

An important object of the invention is to provide an improved apparatus for drilling wells,

which is so constructed that the cutting tool may be inserted in, or removed from, the well for replacement or other purposes, without pulling the entire length of drill pipe which results in a saving of time, labor and expense which is incidental to the removal of the drill pipe.

A particular object of the invention is to provide an improved drilling apparatus including a drill pipe having a drill bit removably supported in its lower end, and an inner, smaller bit de-= pending below said drill bit and serving as a lead bit to guide the drilling of the hole to gauge; both bits being rotated by the rotation of the drill pipe, and both being readily removable from the hole without pulling the entire string of drill pipe prior to the time that the drilling operation begins,

Figure 3 is a transverse, vertical, sectional view showing the parts of Figure 2 in drilling position within the drill pipe,

Figure 4 is a view, partly in elevation and partly in section, of the lower drill collar which carries the cutting blades of the outer bit, said collar being viewed at a right angle from its position as shown in Figure 3,

Figure 5 is. a horizontal, cross-sectional view, taken on the line 5-5 of Figure 4,

Figure 6 is a transverse, vertical, sectional view of the lower end of the drill pipe,

Figure 7 is a bottom view of the drill pipe,

Figure 8 is an elevation of the upper connecting collar which connects the drill pipe with the inner or pilot bit,

Figure 9 is a horizontal, cross-sectional view, taken on the line 9-9 of Figure 1,

Figure 10 is a horizontal, cross-sectional view, taken on the line iii-l0 of Figure 1,

' Figure 11 is a horizontal, cross-sectional view, taken on the line iiil of Figure 1,

Figure 12 is a horizontal, cross-sectional view, taken on the line i2-i2- of Figure 1,

Figure 13 is a horizontal, cross-sectional view, taken on the line Iii-i3 of Figure 3,

Figure it is a vertical, sectional view of a core it bit which may be substituted for the inner bit,

with, and a second bit extending axially through r the drill bit and acting to hold the blades thereof in cuttmg position, said second bit having an improved connection with the drill pipe, whereby rotation is imparted thereto by said pipe.

Still another object of the invention is to provide an improved drilling apparatus, wherein both the inner and outer drill bits may be lowered into, or removed from, the pipe on a wire line or cable, and the drill pipe need neverbe withdrawn whereby said pipe acts as the well casing after the drilling operation is complete.

A construction designed to carry out theim vention will be hereinafter described, together with other features of the invention.

The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawings, in which an example of the invention is shown, and wherein:

Figure 1 is a view, partly in elevation and part- I 7 ly in section, of a drilling apparatus constructed and Figure 15 is a view, partly in elevation and partly in section, of a modified form of connection between the bits.

In the drawings, the numeral it designates a tubular drill pipe which has its upperend connected to the usual square kelly or other drive member (not shown) whereby said pipe may be rotated. The pipe extends downwardly within the well bore and has a bottom drill collar ll threaded on its'lower end. The bottom drill collar is constructed to receive an outer drill bit i2 so as to impart rotation to said bit as the drill pipe and collar are rotated, as will be explained. An inner or pilot bit it extends downwardly through the outer bit I2 and is also rotatably connected with the drill pipe. It will be obvious by observing Figure 1, that with such.

arrangement a rotation of the drill pipe iii through the medium of the kelly (not shown), will impart rotation not onlyto the outer bit l2, but also to the inner or pilot bit it.

The bottom drill collar M is clearly shown in Figures 6 and 7 and this collar is provided with a bore M, which extends substantially throughout the length thereof. The upper end of the bore is threaded at E5 so that the collar may be readily screwed onto the lower end of the drill pipe 19. Near its lower endkthe drill collar is provided with an internal, annular offset or mediate. portion of the body it shoulder it. The construction of the underside direction (Figure 5), it will beobvious that the trailing contact face I I of each notch engages the side of the cutting members 28 whereby a rotareduced and the bottom edge of the drill collar is gradually inclined from this reduced leading side ll of one notch to the enlarged trailing side that the bottom of thedrill collar is formedwith two inclines which connect or extend between the diametrically opposite notches H. To strengthen the construction, the drill collar may be enlarged as shown at l9, theseenlargements being ad- Jacent the notches H. Vertical slots are formed internally of the lower end of the drill collar and lead from the interior of the drill collar above the shoulder it to a point forwardly of the reduced leading face ll of each notch ll. It will be seen that when water or other drilling fluid, is introduced into the drill pipe it and flows downwardly within the drill collar ll, said water or drilling fluid may flow downwardly through the vertical slots it whereby the water will escape at the forward edges or faces of the notches l'l.

As above stated, the drill collar 5 I supports the outer or enlarged drill bit l2 and serves to impart a rotation to this bit. The construction of this bit'is clearly shown in Figures 3, d and 5. The

' bit comprises a tubular body 2! which is provided with an annular external shoulder '22 located slightly below the central portion thereof. A pair of T-shaped slots 23 are cut in the'interabove said tion is imparted to said members. Since the cutting members extend beyond the drillcollar, it y will be seen that a rotation thereof will cause said members to drill thehole.

It is noted that the mounting of the blades 25 within the body 2! is such that said blades are 1e p votally mounted in the body at their upper l8 oithe opposite notch. Thus, it will be seen ends. Since the T-slots 23 extend entirely through the side wall of the body 2!, it is obvious I that the blades may be swung to a retracted posiwith the outer periphery of the body M.

shoulder. and are located diametrically opposite each other. The horizontal leg 26 of each T-slot is disposed slightly above the annular shoulder 22. A pair of cutting blades 25 are provided with outwardly extending arms 26 at their upper ends and each blade is arranged to be supported within the slots 23. As is clearly shown in Figure 4, the extending arms it on the upper end of each blade are positioned within the horizontal portion 2% of the T-slots. The body or vertical portion of the blade depends downwardly through the vertical portion of the T-slot and the length of the blade body is such that the extreme lower end of the blade extends beyond the lower end of the bit body 2|. The extended arms 26 of each blade are held within the T-slots 23; by a suitable retaining member 211, which may be fastened to the body 2! by machine screws 28. It would be possible to weld this retaining memher in place.

The lower end of each blade is provided with I an outwardly extended cutting member 39 (Figure 3). The particular shape of this cutting member is, of course, subject to variation and by observing Figure 5, it will be seen that the cutting members 29 of the blades extend outwardly in a radial direction from the bit body 21. When the bit I! is in position within the drill collar ii, the cutting members 29 of each blade are arranged to engage in diametrically opposite notches ll formed in the bottom of said collar. The top or upper edge'of each cutting member 29 is inclined as shown at 30 and each notch H is provided with a complementary incline 3!. When the cutting blades are located within the notches, the outer and lower edges of said cutting members extend beyond thedrlll collar ll. Theretion whereby the outer surface 'of the cutting members 29 will swing inwardlyso as to lie'flu sh with such arrangement, it is obvious that the blades may be swung inwardly and the body 2! lowered within the drill pipe ill and drill collar H; The body may be dropped or lowered by a cable and when lowered, it will continue a. downward movement until the shoulder 22 on said body strikes the internal annular shoulder it formed within the lower end of the drill collar, as shown in Figure 2. When the shoulder 22 is restingluponthe shoulder it in this manner, it will be manifest that the'cutting members 29 of the blades 25 are spaced from the bottom of the drill collar and this is the initial position of the drill bit prior to the commencement of the drilling.

' It is obvious that since the blades 25 are pivoted at their upper ends to the body 2! that some means must be provided for expanding or swing 'ing the lower ends of the blades outwardly into their cutting position. For this purpose, the indiameter of the mandrel 32 is substantially equal to the mner diameter of the bore of the tubular bit body 2i. Therefore, when the bit I3 and mandrel 32 are lowered through the bit body, it will be obvious that they will serve to expand the cutting blades 26 outwardly at their lower-ends. So long as the mandrel 32 remains within the bit body, it will be obvious that the cutting members :15 will be held in their expanded or cutting posi- For supporting the mandrel 32 and the inner bit l8 within the bit body 2! and also for preventing said mandrel from falling through said body, the mandrel is provided with an external annular collar 33 which is preferably made integral therewith. The lower edge of this collar is arranged to seat on an internal annular shoulder 34 which is formed near the upper end of the body 2i (Figure 3). Thus, when the mandrel and inner bit are lowered within the outer bit l2, such lowering will continue until the lower edge of the collar 33 strikes the shoulder 34 of. the body 2i, at which time further downward movement of the mandrel and its bit it is prevented. From the above, it will be seen that the fore, when the collar is rotated in a clockwise After the bit I? has been lowered to this posiaaeaeee tion (Figure 2), the blades 25 which are pivoted to the body are still in their retracted position since they are hanging or suspended from their pivot point in the horizontal portion M of the T-slots 23. The mandrel 32 and inner bit B3 are then lowered through the drill pipe It and enter the tubular body M of the bit l2. As this occurs, the mandrel and the bit it serve to expand the lower end of the blades 25 and these blades are held in this expanded position so long as said mandrel is located within the body 2!. It is pointed out that the downward movement of the mandrel and inner bit" is limited by the collar 33 on said mandrel striking the internal shoulder M at the upper end of the bit body M. In

the drawings, the mandrel has been shown of such length that the bit It extends below the cutting members 29 of the outer bit it. However, it is noted that the length of this mandrel is subject to variation as it would be possible to have the inner bit it at the same elevation as the cutting members 29 of the outer bit.

For imparting rotation from the rotating drill pipe it to the inner bit it? which is carried by the tubular mandrel 32, a coupling collar dd is connected in the drill pipe. This collar is clearly shown in Figures 2, 3 and 8 and is arranged to be connected with a coupling member A which is carried by the upper end of the mandrel 32. The bore 6! of the collar is preferably of the same diameter as the bore of the drill pipe i and a plurality of notches at are cut in said collar. As clearly shown in Figure 12, four notches are provided but it is to be clearly understood that any desired number may be provided. The top of the notches are bevelled as shown at M and the wall of the bore M of the collar immediately above said bevel M is inclined as shown at t5. An annular shoulder id is provided immediately above the notches 33 and as shown in Figure 8 this shoulder extends between said notches.

The coupling member A which is arranged to be connected with the coupling collar til is constructed in two sections B and C. The lower vertically therethrough. The upper end of this bore is internally threaded at so as to receive the lower threaded end of a tubular shank 56. The shank 5i extends upwardly through an axial bore 52 of the upper member C of said coupling. The upper end of the bore 52 of the member C is enlarged as shown at 53 and the shank is formed with an annular head 5% which is slidable vertically within the enlarged portion 53 of the bore. It is noted that the annular head 54% extends above the shank til as is clearly shown in Figure 3.

The upper end of the bore of the shank Si is formed with an annular bevelled seat 55. With this arrangement, it will be seen that the lower member or section B of the coupling member A is rigidly fastened to the upper end of the mandrel 32. The upper section C of said coupling member is slidable on the tubular shank 5i which is rigidly connected to the lower section and, therefore, the upper section is movable a limited distance with relation to said lower section.

The lower endof the upper section C is provided with a plurality of vertical slots 55 which receive the upper end of elongate vertical dogs 51, which upper end is pivoted therein on a pin 58. The lower ends of the dogs depend from the upper section C and engage in vertical slots 59 which are formed in the lower section B of the coupling. The rear face of each slot 59 is curved upwardly and the extreme lower end of the slot is formed with a shoulder 60 (Figure 3) It is obvious that when the upper section is moved with relation to the lower section with the rear faces of the dogs 51 riding on the rear curved faces of the slots in the lower section B, said dogs will be expanded or retracted depending on which way the upper section C is moved. In other words, if the lower ends of the dogs engage the upper ends of the slots 59 in the lower section B, said dogs will be retracted so that their outer edges do not extend beyond the outer periphery of the lower section B. However, if the upper section C is lowered with relation to said lower section, the rear face of the dog 51 riding on the curved rear face of the slot 59 will be expanded.

The lower end of each dog is formed with an outwardly extending lug 5i and the upper edge of this lug is inclined so as to be complementary with the upper bevelled surface M of the notches 33 in the coupling collar M. The outer side of each dog inclines from the upper: bevelled surface of the lug 57 toward the upper portion of the dog and this inclined surface is complementary to the incline formed above each notch t3 within the collar fit. With such arrangement, it is obvious that when the coupling member A is lowered within the drill pipe ill and the dogs are expanded outwardly into the notches liii of the coupling collar at, a rotation of the drill pipe and collar at will impart a rotation to the coupling member A and mandrel 32 secured thereto. Therefore, it will be seen that the inner bit it carried by the lower end of the mandrel will be rotated through the engagement of the coupling member A with the coupling collar dd. Rotation to the outer bit it, as has been explained, is imparted through the engagements of the cutting members 29 of the blades of said outer bit i2 with the notches it formed in the lower edge of the drill collar ii.

In the operation of the apparatus, the outer or large drill bit i2 is first lowered through the drill pipe and into, the drill collar ii at the lower end thereof. This drill bit may be dropped or lowered by any suitable means, as by a tool engaging an internal annular shoulder 2i which is provided at the upper end of the bit body 2i above the shoulder 36 for this purpose. Any suitable tool which may be suspended from a cable may be employed for engaging beneath this shoulder. Thus, it will be obvious that the bit 82 may be quickly and easily lowered through the drill pipe by a cable. When the bit body 2i enters the collar ll it will be obvious that the external shoulder 22 on said body will engage the internal shoulder i5 provided at the lower end of said collar, whereby further downward movement of the body 2! is prevented. This position of the outer bit it! is clearly shown in Figure 2 and at this time the blades 25 of the bit i2 are in their retracted position since they are hanging from their pivot point within the T-slot 23. The expansion of the blades during the lowering operation is prevented by the outer edges of the cutting members 25 of said blade engaging the inner periphery of the drill pipe and drill collar.

It is noted that when the shoulder is within the drill collar is supporting the bit body 2!, the pivot point of the blades 25 is just above said shoulder it. This causes the lower end of the blades which have the cutter members 29 made integral therewith to be located at some distance below the bottom of the drill collar M. with the bit l2 in this position, it is obvious that the cutting members 28 thereof, being below the bottom of the collar, are not engaging the notches H in the lower end of said collar and, therefore, if the drill pipe is rotated at this time no motion would be imparted to the drill bit l2. After the bit i2 has been lowered within the collar, asabove explained, the inner bit i3 which is carried by the mandrel 82 and which has the coupling member A secured to its upper end is lowered within the drill pipe. This lowering operation may be accomplished by dropping or by the same tool by which the bit 12 has been lowered sincethe coupling member A is provided with a shoulder-42 for receiving a suitable tool at its upper end. Therefore, a cable can be employed in lowering the inner bit It. As the inner bit and the mandrel 32 enter the bore of the bit body 2i, it is obvious that they will serve to expand the blades 25 of said outer bit l2.

It is noted that this expansion takes place at a point below the bottom of the drill collar ll because the outer bit I2 is supported on the annular shoulder is of said collar at this time. The mandrel and inner bit It continue their downward movement until the collar 33 on said mandrel engages the shoulder 34 within the bit body 2 l During the time that the mandrel 32 and bit It are moving downwardly through the body 2|, the coupling member A has moved downwardly through the drill pipe because it is fastened to the upper end of the mandrel 32. It is pointed out that since the tool (not shown) by which the mandrel is lowered is secured to the upper section C of the coupling member A, this upper section C will be separated as far as possible from the lower section B. This is true because the weight of the mandrel and bit is which are secured to the lower section B of the coupling member will pull the shank 5i downwardly until the head 54 of said shank rests on the shoulder 52' formed between the bore 52 and enlarged portion of said bore 53 of the upper section C. Thus it will be seen that the lower section B which carries the mandrel 32 is suspended from the upper section C during the lowering operation. At this time the lugs 51' formed on the lower end of the dogs 51 which are carried by the upper section C are located at the upper end of the slots 59 in the lower section B, whereby said lugs are in their retracted position which permits them to clear the wall or interior of the drill pipe. Therefore, so long as the lowering operation ofthe inner bit and mandrel 22, to-

' gether with the coupling A at the upper end thereof, continues the dogs 5'! are in their retracted position.

The coupling member A is located with relation to the inner bit, and the coupling collar dd is so mounted within the drill pipe Iii, that when the collar 33 on the mandrel 32 strikes the shoulder 34 within the bit body 2!, the coupling member A has moved to the position shown in moved downwardly below the notches 48 which are formed in the coupling collar 40 (Figure 2). At this time a rotation of the drill pipe would not impart a rotation to the inner bit i3 because the lugs 51' are not in engagement with the notches, and similarly no motion would be imparted to the outer bit 82 because the cutting members 29 of the blades 25 of this outer bit are not in engagement with the notches ll formed in the lower end of the drill collar II.

It is noted that while both the inner and outer bits l2 and 88 are being lowered into the drill pipe Iii the bottom of said drill pipe is held off bottom of the hole. Therefore, after the two bits have been positioned as shown in Figure 2, they are in reality suspended from the drill collar ll at the lower end of the pipe Ill. To establish the connections between the drilling collar II and the outer bit l2 and the drill pipe l0 and the inner bit it, it is only necessary to lower the drill pipe id from which said bits are suspended. As this lowering operation continues it will be obvious that eventually the drill bit l3 will strike the bottom of the hole. When this occurs, .the continued lowering of the drill pipe ill will cause the pipe and the coupling collar ll carried thereby to move downwardly with relation to the mandrel 82 and coupling member A carried thereby. The outer drill bit i2 will move downwardly with the drill pipe until such time as this bit strikes the bottom formation and as soon as this occurs this bit will become stationary. 'However, as soon as the inner bit I3 is stopped the lowering of the drill pipe ill will cause the coupling collar 4!) to move downwardly toward the lugs 51' on the outer end of the dogs. The dogs are, of course, engaging the interior wall of the drill pipe just below the coupling collar because the weight of the upper section C of the coupling A is tending to force the dogs downwardly in the slots 59 so that the curved faces of said slots are tending to expand the lower end of the dogs at all times.

As soon as the drill pipe has been lowered a suiiicient distance to permit the notches 43 in the collar Gil-to move opposite the lugs 5'!" of the dogs 51, it will be obvious that said lugs will immediately engage in said slots. In the event that the lugs are not in vertical alinement with the notches 53 it is obvious that the shoulder 46 which is located between each of the notches 83 would strike the upper end of the lugs 51' and would halt any further downward movement of the drill pipe because said pipe would be suspended from the lugs engaging under said shoulder. When this occurred, it would only be necessary to rotate the drill pipe it! slightly in either direction so that the notches 53 would be vertically alined with the, lugs 51'. Thus, it will be seen that the provision of the shoulder 46 provides a positive means for finding the notches 53 with the lugs- 51'. As soon as the lugs are expanded into the notches d3 it will be seen that the weight of the drill pipe is resting on the bevelled upper edge of the lugs 51'. The expanding of the dogs 57 is limited by the inclined face of each dog engaging the inclined surface 45 which is formed above each notch 43 within the collar do.

As is-clearly shown in Figure 3, when the dogs 57 are expanded, the inner bottom edge of said dog is resting on the shoulder bl] which is formed at the lower ends of the vertical slots 59 in the lower section B of the coupling member. In this way, the weight of the drill pipe ii) which is suspended on the bevelled upper edge of the lugs 51,

member A which is carried by the upper end of the mandrel, and therefore, the entire weight of the drill pipe is carried on both the inner bit engagement of the lugs bl in their respective notches 43, the drill collar has moved downwardly with relation to the outer bit i2 which has been held stationary because of its engagement with the formation. As the underside of the drill collar it moves downwardly, it will strike the upper inclined edge 3E9 of the cutting members it of the blades of the outer bit it, If the notches ii in the lower edge of said collar are vertically alined with the cutting members 29 it will be obvious that said cutting members will enter said notches as has been explained. However, in the event that the cutting members are not vertically alinecl with the notches ill, the upper edge of said members will strike the inclined bottom surface or edge of the collar ii. A rotation of the drill pipe id and collar ill will immediately cause the blades to ride into their respective slots.

It will be seen from the above that when the drill pipe has moved downwardly so as to engage the cutting members 29 and the slots ll, and also to engage the dogs 5? of the coupling member A with their respective notches 33, that the parts are in drilling position. The rotation of the drill pipe ill by means of the kelly (not shown) will cause a motion to be imparted through the coupling collar ii] and coupling member A to the mandrel 32 and inner bit It. At the same time the collar H which is rotating with the drill pipe will impart a rotation to the cutting members 29 of the outer bit it because the flat contact faces it of the notches ll will engage the blades and rotate the same. The outer bit will be held in its raised position with relation to the drill col- The provision of the inner bit not only provides a positive means for holding the blades 25 of the lar (Figure 3) so that its cutting members 29 are said cutting members with the formation.

Water, or other drilling fluid, is pumped downwardly through the drill pipe it and is supplied to the inner bit it by passing through the tubular shank 5i of the coupling member A and then downwardly through the tubular mandrel 32 and outwardly through the ports it provided for this purpose in the bit 53. In passing through the outer bit E2, the water passes downwardly around the coupling member A. This coupling member is cylindrical in shape but has its sides flattened as shown at El (Figures 9 and 10) whereby the annular space between this member and the interior of the drill pipe is increased. After flowing downwardly past the coupling member A the water flows around the tubular mandrel 32 and into the annular space i2 between the outer bit body it and the interior of the drill collar ii. From this space the water strikes the internal annular shoulder it of the drill collar andfinally passes out through the vertical slots Ell which are provided in the lower end of said drill collar (Figures 6 and '7). It is noted that the slots 26 are positioned so that the water or other drilling fluid escapes at the forward or leading edge of the notches ll whereby this water washes the leading or forward facev of the cutting membars 29.

outer bit in expanded or cutting position, but also provides a pilot or lead bit which engages the center of the hole. This pilot bit aids in drilling the hole to gauge because it serves as a guide for the outer bit it which does the main cutting. When it is desired to remove the bits for any purpose whatever, it is only necessary to lower a suitable tool (not shown) which will engage beneath the shoulder M in the upper end of the coupling member A. When this is done the drill pipe it is then raised a slight distance so. as to relieve the lugs 5i on the expanded dogs till of the weight of the drill pipe. This causes the lugs to move downwardly within the slots H3 and an upward pull on the upper section C of the coupling member will immediately cause the dogs 5i to be retracted along the inner curved faces of the slots 59 in the lower section B of said member. It is noted that the upward raising of the drill pipe will cause the bottom of the slots tit) to strike the inclined underside of the lugs 5? and due to this inclined surface will tend to help move said dog s inwardly within their slots 59. Thus, it will be seen that the coupling member A, mandrel 32 and inner bit it may be readily removed from mandrel 32 are removed the blades 25 of the outer bit i2 may move inwardly within their slots. Therefore, after the tool has been engaged with the shoulder at the upper end of the bit body it an upward pull thereon will readily remove the entire body it from within the collar ii. I It is pointed out that the-inclination of the upper edge of the cutting members it, as well as the inclination of the underside of the collar i i, will aid in causing the retraction or inward movement of the blades after the mandreltt has been removed from the body. After the body it has been brought to the surface and it is found that the blades 25 need replacing, it is only necessary to remove the retaining plates 27: after which the blades 25 may be readily removed from the 'l'- slots 23. Thus, a new blade may be readily substituted for the worn blade. The inner bit it! may be just as easily removed from the mandrel 32 for replacement or other purposes.

From the above, it will be seen that a drilling apparatus is provided wherein the drill bit is readily removable from or insertable within the drill pipe. The bit may be dropped or quickly lowered within the pipe on a cable and may be just as quickly removed by the same means. During the lowering operation, the retracted cutting blades of the bit cannot move into their expended position because they are held retracted by engagement with the inner wall of the drill pipe. After the outer bit has moved to its lower pasition the inner bit may be lowered by a cable into its proper position. It is pointed out that it would be possible to eliminate the inner bit and to merely lower the mandrel 32 within the outer bit It to hold the blades thereof expanded. In such case, the mandrel would, of course, terminate at a point above the bottom of the cutting members 29. It is obvious that with the above arrangement, it is never necessary to remove the drill pipe from the well in order to replace or change the bits. This results in an enormous saving of time and labor, as well as expense.

fingers lac provided for the purpose. To prevent downward circulation of the drilling fluid through the mandrel 32 and core bit Na, a. ball (not shown) may be dropped through the drill pipe ill so as to engage the seat 55 within the head of the shank 5!, whereby the bore of the mandrel is closed.

Although it is desirable to rotate the outer bit l2 by means of the notches I? provided in the underside or lower edge of the drill collar H, and to rotate the inner or pilot bit l3 through the medium of the coupling collar 40 and the member A, it is not essential, for it would be possible to eliminate either one or the other of these drive mediums. In Figure 15, a modified form of the invention is shown, wherein the coupling mem her A and the coupling collar 40 are eliminated. In this form, the bit body 2| of the outer bit I2 is provided with a plurality of recesses I0 which are disposed vertically and which are located just below the internal shoulder 34 at the upper end of the housing. The collar 33 of the mandrel 32 has lugs II which are arranged to engage within the recesses 10, when the collar 33 is rested on the shoulder 34. With this arrangement, it will be manifest that the drill. pipe ill imparts a rotation to the outer bit and due to the connection between the outer bit and the mandrel 32,. the inner or pilot bit I3 is thereby rotated. 'Iiherefore, by connecting the outer bit housing with the mandrel carrying the inner bit, the coupling A and the coupling collar 40 may be eliminated. Similarly, it would be possible to eliminate the notches II -in the lower edge of the drill collar H and to rotate the inner bit through the coupling A. In suchcase, the connection formed by the lugs II and the slots would impart a rotation from the mandrel 32 of the inner bit to the housing of the outer bit, whereby both inner and outer bits are rotated simultaneously.

The foregoing description of the invention is explanatory thereof and various changes in the size, shape and materials, as well as in the details of the illustrated construction may be made, within the scope of the appended claims, without departing from the spirit of the invention.

parting rotation to the outer bit, and means on the upper end of the mandrel arranged to be connected with the drill pipe for imparting rotation to the inner bit.

2. A drilling apparatus including, a rotatable drill pipe having its lower end open, means for rotating said pipe. an outer bit body adapted to be lowered through the pipe to the bottom thereof and having supporting shoulders formed thereon, cutting blades, each blade being provided with a T-shaped shank, the lateral portion of which is supported on one of said shoulders whereby the blades are pivotally mounted on the body so as to be swung outwardly, said blades normally being held in a retracted position by gravity, means at the bottom of the pipe for supporting the bit body within the pipe so that the cutting blades project from the lower end of the bit, a tubular mandrel adapted to be inserted within the outer bit for swinging the blades outwardly into cutting position, an inner pilot bit caried by the lower end of the mandrel and projecting below the outer bit, means on the lower end of the pipe engaging the blades for imparting rotation to, the outer bit, a coupling in the drill pipe having a plurality of notches therein, and a coupling member on the mandrel having retractible elements arranged to engage said What I claim and desire to secure by Letters Patent is:

1. A drilling apparatus including, a rotatable drill pipe having its lower end open, means for rotating said pipe, an outer bit body adapted to be lowered through the pipe to the bottom thereof and having its outer surface recessed to provide lateral supporting shoulders thereon, cutting blades having their upper ends supported on said shoulders and arranged to be swung outwardly, said blades normally being held in a retracted position by gravity, means at the bottom of the pipe for supporting the bit body within the pipe so that the cutting blades project from the lower end of the bit, a tubular mandrel adapted to be inserted within the outer bit for swinging the blades outwardly into cutting position, an inner pilot bit carried by the lower end of the mandrel and projecting below the outer bit. means on the lower end of the pipe engaging the blades for im-.

notches, whereby the mandrel is coupled to the pipe and rotation is imparted by the inner bit.

3. A drilling apparatus including, a rotatable drill pipe having its lower and open, means for rotating said pipe, an outer bit body adapted to be lowered through the pipe to the bottom thereof and having recesses in its exterior surface to provide supporting shoulders thereon, cutting blades, each blade having a vertical shank provided with a laterally extending arm at its upper end, the arm of each shank being supported on one of the shoulders on the body, whereby the blades are pivotally mounted on the body and may be swung outwardly, said blades'normally being held in a retracted position by gravity, means at the bottom of the pipe for supporting the bit body within the pipe so that the cutting blades project from the lower end of the bit, a tubular mandrel adapted to be inserted within the outer bit for swin ing the blades outwardly into cutting position, an inner pilot bit carried by the lower end of the mandrel and projecting below the outer bit, means on the lower end of the pipe engaging the blades for imparting rotation'to the outer bit, a coupling in the drill pipe having a plurality of notches therein, a coupling member on the mandrel having retractible elements arranged to engage said notches, whereby the mandrel is coupled to the pipe and rotation is imparted to the inner bit, and means for conducting a. drilling fluid downwardly through the drill pipe and directing said fluid onto the cutting blades of both the inner and outer bits during the rotation thereof.

4. A drilling apparatus including, a rotatable drill pipe, means for rotating said pipe, an outer cutter bit having expansible blades adapted to be lowered through the pipe to the bottom thereof, means at the lower end of the pipe for supporting the bit at the bottom thereof, a mandrel adapted to be inserted within the outer bit for expanding the blades of said bit into cutting position, an inner pilot bit carried by the lower end of the mandrel and projecting below the outer bit, the lower end of the drill pipe having vertical shoulders thereon and having its lower edge inclined away from said shoulders, whereby when the blades of said outer bit are expanded and moved into engagement with said lower edge, said blades are guided into contact with the shoulders so that rotation of the pipe will rotate the outer bit, and means for connecting the mandrel directly to the pipe whereby the inner bit is also rotated upon rotation of the pipe.

5. A drilling apparatus including, a rotatable drill pipe, means for rotating said pipe, an outer cutter bit having expansible blades adapted to be lowered through the pipe to the bottom thereof, means at the lower end of the pipe for supporting the bit at the bottom thereof, a mandrel adapted to be inserted within the outer bit for expanding the blades of said bit into cutting position, an inner pilot bit carried by the lower end of the mandrel and projecting below the outer bit, the lower end of the drill pipe having vertical shoulders thereon and having its lower edge inclined away from said shoulders, whereby when the blades of said outer bi-t are expanded and moved into engagement with said lower edge, said blades are guided into contact with the shoulders so that rotation of the pipe will rotate the outer bit, means for connecting the mandrel directly to the pipe whereby the inner bit is also rotated upon rotation of the pipe, and means for conducting a drilling fluid downwardly through the drill pipe and directing said fluid onto the cutting blades of both the inner and outer bits during the rotation thereof.

6. A drilling apparatus including, a rotatable drill pipe, means for rotating said pipe, an outer cutter bit having expansible blades adapted to be lowered through the pipe to the bottom thereof, means at the lower end of the pipe for supporting the bit at the bottom thereof, a mandrel adapted to be inserted within the outer bit for expanding the blades of said bit into cutting position, an inner pilot bit carried by the lower end of the mandrel and projecting below the outer bit, the lower end of the drill pipe having vertical shoulders thereon and having its lower edge inclined away from said shoulders, whereby when the blades of said outer bit are expanded and moved into engagement with said lower edge, said blades are guided into contact with the shoulders so that rotation of the pipe will rotate the outer bit, a coupling in the drill pipe having a plurality of notches therein, and a coupling member on the mandrel having retractible elements arranged to engage said notches, whereby the mandrel is coupled to the pipe and rotation .is imparted to the inner bit.

7. A drilling apparatus including, a rotatable drill pipe, an outer cutter bit adapted to be lowered through the pipe to the bottom thereof, said bit comprising a tubular body having expansible blades suspended from the exterior surface of said body, whereby the blades may swing radially outwardly from the body, means at the lower end of the drill pipe for supporting the bit and disposed so as to support the bit with the blades thereof projecting from the lower end of the pipe, a mandrel adapted to be separately lowered into the outer bit after the latter has been lowered and landed in the drill pipe and co-acting with the blades of the bit for expandlng said blades radially outwardly while said blades are below the lower end of the drill pipe, an inner pilot bit carried by the lower end of the mandrel and lowered therewith so as to project below the outer bit blades, and connecting means adapted to efiect a connection between the drill pipe and the outer and inner bits, said connection being in a disengaged position when the outer bit is landed in the drill pipe and the mandrel and inner bit is extending through said outer bit, said connecting means being moved to an engaged position to effect a connection between the drill pipe and the outer and inner bits upon a relative downward movement of the drill pipe with respect ltO said bits.

8. A drilling apparatus including, a rotatable drill pipe, an outer cutter bit adapted to be lowered through the pipe to the bottom thereof, said bit comprising a tubular body having expansible blades suspended from the exterior surface of said body, whereby the blades may swing radially outwardly from the body, means at the lower end of the drill pipe for supporting the bit and disposed so as to support the bit with the blades thereof projecting from the lower end of the pipe, a, mandrel adapted to be separately lowered into the outer bit after the latter has been lowered and landed in the drill pipe and co-acting with the blades of the bit for expand.- ing said blades radially outwardly While said blades are below the lower end of the pipe, an inner pilot bit carried by the lower end of the mandrel and lowered therewith so as to project below the outer bit blades, means on the lower end of the drill pipe for imparting rotation to the outer bit upon rotation of the pipe located to be engaged by the expanded blades when the drill pipe is lowered relative to the outer bit to move the support away from said bit, and means for connecting the upper end of the mandrel with the drill pipe, said connection being effected upon downward movement of the drill pipe with relation to the mandrel pipe after the said mandrel has been lowered to expand the blades of the outer bit.

9. A drilling apparatus including, a rotatable drill pipe, an outer drill bit adapted to be dropped or lowered through the pipe to the bottom thereof, said bit comprising a tubular body having slots therein and also having expansible blades mounted on the exterior of the body, said blades being freely movable within the slots radially of the body, an inwardly extending projection within the lower end of the pipe for limiting the downward movement of the outer bit, whereby the bit is supported in a predetermined position within the pipe, a mandrel independent of the outer bit and adapted to be lowered through the pipe and through the bit after said bit is in position within the pipe, said mandrel co-acting with the blades to expand the same radially outwardly into a cutting position, an inner pilot bit.

position to effect a connection between the drill pipe and the outer and inner bits upon a relative downward movement of the drill pipe with respect to said bits.

JAMES F. CHAPPELL. 

